This invention relates to a cathode busbar structure for electrolytic cells suited for the electrolysis of aqueous solutions. More particularly, this invention relates to a cathode busbar structure for electrolytic cells suited for the electrolysis of aqueous alkali metal chloride solutions.
Electrolytic cells have been used extensively for many years for the production of chlorine, chlorates, chlorites, hydrochloric acid, caustic, hydrogen and other related chemicals. Over the years, such cells have been developed to a degree whereby high operating efficiencies have been obtained, based on the electricity expended. Operating efficiencies include current, decomposition, energy, power and voltage efficiencies. The most recent developments in electrolytic cells have been in making improvements for increasing the production capacities of the individual cells while maintaining high operating efficiencies. This has been done to a large extent by modifying of redesigning the individual cells and increasing the current capacities at which the individual cells operate. The increased production capacities of the individual cells operating at higher current capacities provide higher production rates for given cell room floor areas are reduce capital investment and operating costs.
In general, the most recent developments in electrolytic cells have been towards larger cells which have high production capacities and which are designed to operate at high current capacities while maintaining high operating efficiencies. Within certain operating parameters, the higher the current capacity at which a cell is designed to operate, the higher is the production capacity of the cell. As the designed current capacity of a cell is increased, however, it is important that high operating efficiencies be maintained. Mere enlargement of the component parts of a cell designed to operate at low current capacity will now provide a cell which can be operated at high current capacity and still maintain high operating efficiencies. Numerous design improvements must be incorporated into a high current capacity cell so that high operating efficiencies can be maintained and high production capacity can be provided.
In mere scaling up of existing electrolytic cell hardware, problems are encountered in current distribution to the cell. The solution of additional or larger busbars, although not economic, is also not feasible because of the amount of welding of large sections of metals and cracking of welds because of slight vibrations together with the weight of the components which are welded together.
Because the present invention may be used in many different electrolytic cells of which chlor-alkali cells are of primary importance, the present invention will be described more particularly with respect to chlor-alkali cells and most particularly with respect to chlor-alkali diaphragm cells. However, such description are not to be understood as limiting the usefulness of the present invention with respect to other electrolytic cells.
In the early prior art, chloro-alkali diaphragm cells were designed to operate at relatively low current capacities of about 10,000 amperes or less and had correspondingly low production capacities. Typical of such cells is the Hooker Type S Cell, developed by the Hookers Chemical Corporation, Niagara Falls, New York, U.S.A., which was a major breakthrough in the electrochemical art at its time of development and initial use. The Hooker Type S Cell was subsequently improved by Hooker in a series of Type S cells such as the Type S-3, S-3A, S-3B, S-3C, S-3D and S-4, whereby the improved cells were designed to operate at progressively higher current capacities of about 15,000 20,000, 25,000, 30,000, 40,000 and upward to about 55,000 amperes with correspondingly higher production capacities. The design and performance of these Hooker Type S cells are discussed in Shreve, Chemical Process Industries, Third Edition, Page 233 (1967), McGraw-Hill; Mantell, Industrial Electrochemistry, Third Edition, Page 434 (1950), McGraw-Hill; and Scone, Chlorine, Its Manufacture, Properties and Uses, A.C.S. Monograph, Pages 94-97 (1962). Reinhold. U.S. Pat. No. 2,987,463 by Baker et al., issued June 6, 1961, to Diamond Alkali discloses a chloralkali diaphrarm cell designed to operate at a current capacity of about 30,000 amperes which is somewhat different than the Hooker Type S series cells. U.S. Pat. Nos. 3,464,912 by Emery et al., issued Sept. 2, 1969, to Hooker and 3,493,487 by Currey et al. issued Nov. 2, 1971 to Hooker disclose chlor-alkali diaphragm cells designed to operate at a current capacity of about 60,000 amperes.
The above description of the prior art shows the development of chlor-alkali diaphragm cell design to provide cells which operate at higher current capacities with correspondingly high production capacities. Chlor-alkali diaphragm cells have now been developed which operate at high current capacities of about 150,000 amperes and upward to about 200,000 amperes with correspondingly higher production capacities while maintaining high operating efficiencies.
Electrolytic cells operating at such high current require an efficient distribution system in order to avoid heating or the buildup of heat in localized areas which may cause malfunction of the cell.
In the normal operation of a plant utilizing electrolytic cells, the removal of a single cell from a circuit of cells is required to service the cell removed from the circuit. When this is done the cell so removed is skipped or jumpered and the current is directed around that cell by electrically connecting the two adjacent cells. Although that is usually a temporary arrangement, until the problem with the jumpered cell is remedied, the high current being utilized requires an efficient current distribution system to be used in the cells being connected in the jumpering operation; otherwise the problem of localized heat or heat buildup occurs and may result in a rapid malfunction of the cells affected.
The cathode busbar structure of the present invention provides an efficient current distribution both during normal cell operation or during jumpered operation.